Quantification of ? phase strengthening in titanium alloys: Crystal plasticity model incorporating ?/? heterointerfaces

A strategy to quantify the second phase strengthening of alpha precipitates in titanium alloys is proposed to predict the mechanical performance through crystal plasticity finite element (CPFE) models. Considering the different dominant features of equiaxed and lamellar microstructures, statistical and microstructural factors are introduced to describe the slip resistance variations in the beta matrix. The significant contribution of the interfaces is incorporated by introducing the interface-affected zone (IAZ) into crystal plasticity constitutive laws of equiaxed microstructures. In particular, the slip resistance variation is derived accounting for the interfacial energy distri-bution inside the IAZ. Meanwhile, the arrangement of the alpha lamellae is more compact and complex than that of spherical alpha grains in equiaxed microstructures; thus, instead of the IAZ, the interface length density is applied to describe the strengthening effects of the interfaces in lamellar microstructures. The elastic interaction energy induced by the semi-coherent interfaces of lamellae is obtained according to the micro-elastic theory. Using the advantages of the aforementioned improved models, CPFE simulations of the tensile behavior of equiaxed and lamellar microstructures at room temperature are performed, with the results matching well with the experimental data. Moreover, differences regarding the lattice structures and grain orienta-tions lead to non-uniform strain partitioning in equiaxed and lamellar microstructures. Equiaxed alpha grains that favor prismatic slip tend to bear more plastic deformation than those favoring basal slip. The growth direction of alpha lamellae affects the deformation ability as well. Consequently, the proposed approach can precisely predict the mechanical properties of dual-phase titanium alloys through statistical values of microstructural features, and can be utilized in the investigations of other metals with similar structural characteristics.

Automated summary

A strategy to quantify the second phase strengthening of alpha precipitates in titanium alloys is proposed in this study, which can accurately predict the mechanical performance through crystal plasticity finite element models. Statistical and microstructural factors are introduced to describe the slip resistance variations in the beta matrix, with the concepts of interface-affected zone and interface length density being applied to equiaxed and lamellar microstructures respectively.